Ans: D
Since $P$ is a moving point such that the perpendicular distance from $P$ to $L$ is $3$, then the locus of $P$ is a pair of straight lines, one is above $L$ and the other is below $L$.
Since $P$ is a moving point such that the perpendicular distance from $P$ to $L$ is $3$, then the locus of $P$ is a pair of straight lines, one is above $L$ and the other is below $L$.
